Angle-resolved photoemission spectroscopy of SrCuO₂: Spin-charge separation?

We have performed angle-resolved photoemission spectroscopy (ARPES) on SrCuO₂, which consists of two parallel Cu-O chains, to study the "spin-charge separation" in a strongly correlated one-dimensional (1D) system. We observed two dispersive bands in the vicinity of the Fermi level (E_F) in the chain direction. One shows a small energy dispersion of about 0.2 eV while the other has a dispersion of more than 0.8 eV. Both have a maximum common point at about 0.9 eV binding energy at k = π/2 (where k is the wave vector) in the Brillouin zone. The two dispersive bands may be ascribed to the "spinon" and "holon" bands, respectively, produced through the separation of spin and charge freedoms in the 1D Cu-O chain. The experimental result shows good qualitative agreement with the model calculations, but shows quantitative disagreement in the intensity of the spinon and holon bands. In the perpendicular direction, we observed a small energy dispersion of about 50 meV with a maximum point at k = π, which indicates a finite interchain interaction in SrCuO₂.